As is well known in the art, an integrated circuit (IC) die, also referred to as an chip, typically contain an active device layer formed on a hulk silicon substrate and a metallization layer formed on the active device layer. The active device layer contains the active circuitry formed using a large number of transistors. The active circuitry may be, for example, logic circuitry for an IC chip that is used as a processor. The metallization layer is formed using several layers of insulated metal lines that interconnect the transistors in the active device layer. These metal lines are generally referred to as metal interconnects. A passivating layer is generally formed over the metal interconnects and copper bumps are formed atop the passivation layer that couple the metal interconnects to external devices. The copper bumps are often controlled-collapse chip connections (C4 bumps).
The backside surface of the integrated circuit die, opposite the C4 bumps, is generally not used for any functional purpose. In some embodiments the backside surface may be polished using a chemical mechanical polishing process to remove a portion of the bulk silicon substrate material and thereby reduce the thickness of the IC die. Aside from that, the backside of the IC die generally remains unused.